1. Field of the Invention
This invention is in the field of fluid flow heat exchangers in which potentially corrosive fluid flows through heat exchange tubes whose ends extend through and are secured to tubesheets. This invention pertains particularly to tube plugs for plugging the open ends of damaged heat exchange tubes.
2. Discussion of the Prior Art
In connection with leaking heat exchanger tubes, plugging damaged and leaking heat exchange tubes is the most common method of taking the tubes out of service. This is normally done by inserting a conventional one or two-piece tapered plug into the end of a damaged heat exchange tube.
A plugged tube may become filled with shell side fluid that becomes stagnant in the annular space between the outer surface of the plug and the inner surface of the tube, especially at the six o'clock or bottom dead center position. Such stagnant fluid can cause severe corrosion to the internal surface of the tube, and such corrosion can eventually penetrate to the tubesheet and cause severe damage to the tubesheet.
A conventional fluid heat exchanger 1 is illustrated in FIGS. 1, 2A and 2B showing tubesheets 4A, 4B and heat exchange tubes 3a, 3b, 3c and 3d with their ends secured in tubesheets 4A, 4B by conventional hydraulic expansion, seal welding or other means. FIG. 3 shows how a tube damaged from cracks, pin holes or other issues can be taken out of service using a prior art one-piece tapered plug 24. Such plugs are commonly used in the petroleum and petrochemical industries due to the ease of fabrication and installation. This tube plug action is normally taken when it is not practical, due to production cost impact, to take the entire heat exchanger out of service in order to replace damaged tubes. Sealing of such a heat exchange tube and tube plug connection is achieved by the friction fit between the plug and the internal or bore surface of the tube.